Method of installing a screw-type anchor

Abstract

The method of securely placing a screw-type anchor in the earth without unduly disturbing the surrounding soil, including the step of enveloping the anchor's shank in a special tubular mandrel. The mandrel has a helical flight near its bottom end, with a pitch that is substantially the same as the anchor's flight, such that the mandrel's flight constitutes an effective extension of the anchor's flight. When the anchor/mandrel combination is rotated in a first direction, the two elements will burrow as a unit into the ground. After the mandrel has been rotated sufficiently to put the anchor at a designed depth in the earth, rotating the mandrel in the opposite direction causes it to separate from the anchor and back out of the earth through substantially the same cut that was made when the anchor was turned into the earth. A preferred manner of applying torque to the mandrel is to utilize an electrically powered portable torque unit, in which the direction of rotation (clockwise or counterclockwise) is selectable by manually flipping a switch. Torque reaction loads from the portable torque unit are preferably passed to the earth through a mobile frame which is rolled to the installation site on wheels or the like.

What is claimed is: 
     
       1. The method of securely placing a screw-type anchor in the earth without unduly disturbing the surrounding soil, said anchor having a shank and a flight of given pitch, comprising the steps of: a. enveloping the anchor's shank in a tubular mandrel, said mandrel having a flight near its bottom end of substantially the same pitch as the anchor's flight, with the mandrel's flight constituting an effective continuation of the anchor's flight;   b. placing the tip of the anchor in contact with the earth and rotating the anchor in a direction to cause its entrance into the earth, with anchor rotation being accomplished by rotating the enveloping mandrel so as to apply torsional loads to the anchor near the anchor's flight; and   c. after the anchor has been rotated sufficiently to achieve a desired depth in the earth, rotating the mandrel in the opposite direction to cause it to separate from the anchor and to back out of the earth through substantially the same cut that was made when the anchor was turned into the earth.   
     
     
       2. The method as claimed in claim 1 wherein the leading edge of the mandrel's flight is positioned so as to abut the trailing edge of the anchor's flight, so that rotating the mandrel can impart a torsional load on the anchor through the anchor's flight. 
     
     
       3. The method as claimed in claim 1 wherein torque reaction loads recited in the two rating steps are passed to the earth through a mobile frame. 
     
     
       4. The method as claimed in claim 1 wherein an electrically powered portable torque unit is employed to rotate the mandrel, and the direction of rotation is reversible by manually flipping a switch, whereby the mandrel can be extracated from the earth without physically disconnecting the torque unit from the mandrel.